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Megafauna are important seed dispersers because they can disperse large quantities of seeds over long distances. In Hokkaido, Japan, the largest terrestrial animal is the brown bear (Ursus arctos) and other megafauna seed dispersers are lacking. Thus, brown bears are expected to have an important function as seed dispersers in Hokkaido. In this study, we, for the first time, evaluated the seed dispersal function of brown bears in Hokkaido using three fleshy-fruited trees and studied: (1) gut passage time (GPT) in feeding experiments, (2) seed dispersal distance using tracking data of wild bears, and (3) the effect of gut passage and pulp removal on germination rate. Most seeds were defecated intact, and less than 6% were broken. The average GPT without pulp was 3 h and 56 min to 6 h and 13 min, depending on the plant and trial. Each plant’s average simulated seed dispersal distance was 202–512 m. The dispersal distance of Actinidia arguta seeds with pulp was significantly longer than those without pulp because of their longer GPT. The germination rate of defecated seeds without pulp was 19–51%, depending on the plant, and was significantly higher or not different comparing with that of seeds with pulp. We concluded that brown bears in Hokkaido are effective seed dispersers. In managing brown bears in Hokkaido, such ecological functions should be considered along with conserving the bear population and reducing human–bear conflicts.

Human habituation of large carnivores is becoming a serious problem that generates human–wildlife conflict, which often results in the removal of animals as nuisances. Although never tested, human habituation potentially reduces the fitness of adult females by reducing their offspring’s survival as well as their own, due to an increased likelihood of human-caused mortality. Here, we tested this hypothesis in brown bears inhabiting Shiretoko National Park, Japan. We estimated the frequency of human-caused mortality of independent young (aged 1–4 years) born to mothers living in areas with different maternal levels of human habituation and different proximities to areas of human activity. The overall mortality rate was higher in males than in females, and in females living near a town than those in a remote area of park. Surprisingly, more than 70% of males born to highly habituated mothers living around a remote wildlife protection area were killed by humans; this proportion is greater than that for males born to less-habituated mothers living in almost the same area. The current study clarified that interactions among maternal human habituation, birthplace (proximity to town), age, and sex determine the likelihood of human-caused mortality of brown bears at an early stage of life.

Understanding individual variations in animal behavior is crucial for ecology, evolution, conservation, and wildlife management. However, traditional bio‐logging methods have often impeded the reconstruction of long‐term behavioral patterns in mammals because of cost, battery life, and device size constraints. This study proposes and evaluates a novel method using retrospective isotope analysis of eye lenses to reconstruct mammalian feeding history, focusing on brown bears (Ursus arctos). We devised a protocol for longitudinal segregation of fragile mammalian lenses and sequentially analyzed lens fragments for carbon and nitrogen stable isotope ratios (δ13C and δ15N, respectively) in seven bears. We verified the reproducibility of the protocol by comparing isotopic patterns within lens pairs of the same bear. The results successfully reconstructed time‐series feeding histories, capturing dietary shifts during the lactation‐weaning process, reflected by δ15N from all bears and changes in corn crop (Zea mays) consumption primarily indicated by δ13C from nuisance bears. The reconstructed δ15N lactation‐weaning signal suggested that higher‐resolution isotopic information is preserved for 1–2 years after birth, with resolution declining as eye lens growth slows. The similarity of patterns between the same lens pairs supports the reliability of the method. This novel approach for reconstructing the time‐series feeding history of various mammals is simple and effective.

Natal dispersal likely plays an important role in avoiding inbreeding among large carnivores. We tested the hypothesis that male-biased dispersal reduces close inbreeding by limiting the spatial overlap of opposite-sex pairs of close relatives in brown bears (Ursus arctos) in the Shiretoko Peninsula, Hokkaido, Japan. We genotyped 837 individuals collected in 1998–2017 at 21 microsatellite loci and performed parentage analysis. To calculate natal dispersal distance, we considered the site where the mother was identified as the birthplace of her offspring, and the site where the offspring were identified as their dispersed place. As predicted, we found that dispersal distances were significantly greater for males (12.4 km ± 1.0) than for females (7.7 km ± 0.9), and those for males increased from 3 years old, indicating that males begin to disperse around the time sexual maturation begins. Relatedness decreased with distance among pairs of females, and the mean relatedness was significantly higher between pairs of females than between pairs of males or between female–male pairs within 3 km. Closely related female–male pairs rarely (5–6%) resided in close proximity (< 3 km), compared with pairs of closely related females. Our study revealed that the potential for close inbreeding was low in Hokkaido brown bears because males are effective dispersers.

Understanding natal dispersal patterns is fundamental in the ecology and conservation biology of large wild carnivores. In this study, we used two approaches to determine genetic variation and dispersal patterns of brown bears in the Shiretoko Peninsula, eastern Hokkaido, Japan. The first approach was a large-scale genetic analysis. We analyzed haplotypes from the mitochondrial DNA (mtDNA) control region of 760 individual samples collected throughout the peninsula during 1998–2016. We detected seven haplotypes, including two that were confirmed for the first time. In females, the distribution of haplotypes was geographically structured, whereas haplotypes in males were distributed widely throughout the peninsula. Only some males in the lower peninsula had haplotypes that were not detected within the peninsula. The second approach was a local-scale genetic analysis, including intensive focal sampling in the Rusha area, a special wildlife protection area on the peninsula. Proportions of mtDNA haplotypes in adult bears were investigated and compared between the sexes. Although more than half of the females had the same haplotype, males had more diverse haplotypes, suggesting that they came to the Rusha area from other regions. Thus, our study revealed that mtDNA haplotype distribution has been maintained by female philopatry, and that bears exhibit male-biased dispersal. Furthermore, the lower peninsula appears to act as a contact zone between the peninsula and mainland Hokkaido, which is important for maintaining genetic diversity.

The reproductive tracts of 130 adult female brown bears (Ursus arctos) in Hokkaido, Japan, euthanized during 2010–2013 for conflict management, were examined for the presence and number of corpora lutea (CL) in the ovary and placental scars (PS) in the uterine horns. We scored PS on a 0–5 scale based on morphological features including their rim and color. They were characterized as representing either current-year parturition, as determined by accompanying cubs, or previous-year parturition, as determined by accompanying yearlings. In total, 128 females were divided into 3 reproductive categories: 44 females with current-year parturition, 39 with previous-year parturition, and 45 solitary females that had not given birth for >2 years. The estimated ovulation rate was 2.21 ± 0.55 (mean ± SD), the implantation rate was 1.91 ± 0.74, and the litter size was 1.54 ± 0.51. Implantation rates were lower than ovulation rates and changed annually during 2010–2013. Systematic observation of PS and CL allowed us to evaluate the reproductive history and parameters in Hokkaido brown bears and ascertain their annual variation.

Robust estimates of demographic parameters are critical for effective wildlife conservation and management but are difficult to obtain for elusive species. We estimated the breeding and adult population sizes, as well as the minimum population size, in a high‐density brown bear population on the Shiretoko Peninsula, in Hokkaido, Japan, using DNA‐based pedigree reconstruction. A total of 1288 individuals, collected in and around the Shiretoko Peninsula between 1998 and 2020, were genotyped at 21 microsatellite loci. Among them, 499 individuals were identified by intensive genetic sampling conducted in two consecutive years (2019 and 2020) mainly by noninvasive methods (e.g., hair and fecal DNA). Among them, both parents were assigned for 330 bears, and either maternity or paternity was assigned to 47 and 76 individuals, respectively. The subsequent pedigree reconstruction indicated a range of breeding and adult (≥4 years old) population sizes: 128–173 for female breeders and 66–91 male breeders, and 155–200 for female adults and 84–109 male adults. The minimum population size was estimated to be 449 (252 females and 197 males) in 2019. Long‐term continuous genetic sampling prior to a short‐term intensive survey would enable parentage to be identified in a population with a high probability, thus enabling reliable estimates of breeding population size for elusive species. This study estimated the breeding and adult population sizes, as well as the minimum population size, in a high‐density brown bear population on the Shiretoko Peninsula, in Hokkaido, Japan, using DNA‐based pedigree reconstruction. This study showed that combination of a short‐term intensive genetic survey and long‐term continuous genetic sampling prior to it enables parentage to be identified in a population with a high probability, thus enabling reliable estimates of breeding population size for elusive species.

The reproductive tracts of 130 adult female brown bears (Ursus arctos) in Hokkaido, Japan, euthanized during 2010-2013 for conflict management, were examined for the presence and number of corpora lutea (CL) in the ovary and placental scars (PS) in the uterine horns. We scored PS on a 0–5 scale based on morphological features including their rim and color. They were characterized as representing either current-year parturition, as determined by accompanying cubs, or previousyear parturition, as determined by accompanying yearlings. In total, 128 females were divided into 3 reproductive categories: 44 females with current-year parturition, 39 with previous-year parturition, and 45 solitary females that had not given birth for >2 years. The estimated ovulation rate was 2.21 ± 0.55 (mean ± SD), the implantation rate was 1.91 ± 0.74, and the litter size was 1.54 ± 0.51. Implantation rates were lower than ovulation rates and changed annually during 2010-2013. Systematic observation of PS and CL allowed us to evaluate the reproductive history and parameters in Hokkaido brown bears and ascertain their annual variation.

Investigating individual behavioural variations in mammals is essential for understanding their ecology and evolution, and plays a critical role in conservation and management practices. However, the reconstruction of long-term individual behaviour, such as via bio-logging, remains challenging owing to cost constraints and limitations of battery life and the impact of device size for smaller animals. This study proposed and tested a novel and cost-effective method for retrospective isotope analysis using mammalian eye lenses, specifically focusing on brown bears (Ursus arctos). Seven pairs of bear eye lenses were collected from southwestern Hokkaido, Japan. One or both lenses of each bear were segregated into small fragments from the outermost to the core tissues, and the nitrogen and carbon stable isotope ratios (δ15N and δ13C) of each eye lens fragment were measured. These isotope ratios in the eye lenses were compared with the δ15N and δ13C of potential brown bear diets in the study region (C3 herbs, C3 fruits, terrestrial animals, and corn). Additionally, we compared the isotopic patterns in both the right and left lenses of the same bear in two individuals to evaluate the consistency of our preparation protocol. In all eye lenses, high δ15N values were identified near the core, which gradually decreased towards the outer tissues, indicating ontogenetic dietary shifts related to lactation and weaning in the early life stage. Bears from study areas with high corn availability exhibited substantial increases in δ13C and δ15N in the outer lens tissues, suggesting a dietary shift toward corn consumption after weaning. Isotopic patterns between lens pairs from the same individual were similar, although discrepancies increased in tissues located 1.00 to 2.25 mm from the core, highlighting the need for standardisation in sample processing. This study demonstrates a novel and simple technique for retrospective isotope analysis in wild mammals using eye lenses, effectively reconstructing the feeding histories of brown bears. Our findings provide a new avenue for studying individual time-series behavioural patterns, with important implications for the fields of mammalian ecology, evolution, conservation, and management.Competing Interest StatementThe authors have declared no competing interest.